If each member of two groups, such as a group of suppliers and a group of buyers, or a group of students who want to get a job and a group of companies which wants to get an employee, wants to make a pair with a particular member of the other group, the member whom he or she wants to make a pair with does not necessarily have him or her at the first priority on the list of whom the member wants to make a pair with him or her. Therefore, as a method for letting each of members as many as possible to make a pair with whom the member wants to make a pair, a method for each member in the two groups to order the members of the other groups and make a matching between the groups based on the priority list of each member is known. Specifically, according to a stable matching (see Non-Patent Document 1) presented in the paper by Gale and Shapley in 1962, so-called a blocking pair cannot be made.
It is not preferable to let members of the group know the contents of his or her priority list or the result of his or her matching, even in order to make a matching. As a solution to this problem, a third party provides a matching service can be considered. Each member sends his or her priority list to a service provider. The service provider, in turn, performs the matching based on the priority list of each member and then informs the member on the matching result. The priority list and the matching result, however, are confidential information, which are ones of the most important kind of information for the company and sensitive information for the individual. Thus, the both sides want to hide the information also from the third party.
As a conventional technique for enabling a party to confidentially get the information which is to be confidential, a technique for providing a mediating institute between an information providing institute and a user who is provided with information, letting the information providing institute provide the information for the user via the mediating institute and encrypting the information to be dealt by the mediating institute so as not to be decrypted by the mediating institute (see Patent Document 1).
[Non-Patent Document 1] “College Admissions and the Stability of Marriage”, written by D. Gale and L. S. Shaplery, American Mathematical Monthly, 69th volume, 1962, pages 9-14    [Patent Document 1] Published Unexamined Patent Application No. 2003-18142
Even if a user is enabled to get confidential information by hiding destination information on the user from the service provider by using the abovementioned technique, the contents of the priority list that is required for making matching cannot be hidden from the service provider, letting the service provider identify the user at last from a priority list collected from each member. Then, a method for allocating ID for each member, allowing only the member of the group to know relationship between the members and the IDs and sending a priority list of IDs to the service provider can be considered.
In the abovementioned case, whether the contents of the priority list or the matching result can be kept confidential or not depends on each member's management of the information indicating relationship between the members and IDs. If the information indicating the relationship between the members and IDs is leaked to the outside of the group, the service provider gets to know the contents of the priority list and the matching result and also identify the user. If a computer for a service provider is hacked, the information is further leaked to a third party. It is difficult to make all the members of the group to keep security management to avoid such an incident.
Then, the present invention intends to provide a device, a method and a program for providing a highly secured matching service that hides the contents of a priority list and a matching result from a service provider and a third party even if relationship between a member and his or her ID is leaked outside.